The use of identification documents and other credentials is pervasive. Credentials are used on a daily basis for a number of different purposes. Credentials, which may also be referred to as secure documents, are most commonly used to prove identity, to verify age, to access an asset (e.g., secure area, financial account, computing resource, etc.), to evidence driving privileges, to cash a check, and so on. Airplane passengers are required to show a credential during check in, and sometimes at security screening and prior to boarding their flight. We also live in an ever-evolving cashless society where credentials are used to make payments, access an automated teller machine (ATM), debit an account, or make a payment, etc. Many industries require that their employees carry photo identification credentials on the job and to access various locations on a job site.
While many different types of security features have been developed to enhance the security associated with credentials, optical or holographic security features have been among the most popular features developed in the last decade thanks to their difficulty to copy and the ease with which they can be verified. The diffractive effects of surface relief structures is known. However, traditional methods of producing diffractive effects are inefficient in most cases.